Method and apparatus for developing latent images



A. GAMES Aug. 9, 1966.

METHOD AND APPARATUS FOR nnvswrma LATENT mmzs Filed Jan. 17, 1963 3 Sheets-Sheet 1 A GAMES Aug. 9, 1966 METHOD AND APPARATUS FOR DEVELOPING LATENT IMAGES 3 Sheets-Sheet 2 Filed Jan. L7, 1963 8- 9, 1966 A. GAMES 3,265,522

METHOD AND APPARATUS FOR DEVELOPING LATENT IIAGES iled Jan 1'7, 195s p v a sheets-sheet a METHOD AND APPARATUS FOR DEVELOPING LATENT IMAGES Abraham Games, London, England, assignor to Image Limited, London, England, a British company Filed Jan. 17, 1963, Ser. No. 252,239 Claims priority, application Great Britain, Jan. 25, 1962, 2,870/ 62 18 Claims. (Cl. 117-25) This invention relates to the copying of originals. For example, the originals may take the form of printed matter, pictorial designs, photographs and so forth. It is particularly concerned with a form of copying process as set forth in my copending application Serial No. 6,546, filed Feb. 3, 1960, which is assigned to the assignee of the present application.

In my prior application a process and apparatus are described in which a vaporizing agent is caused to evaporate from the surface of an original to be copied and then to condense on a copy surface over areas representative of the original design to form a latent image. In most cases this latent image is developed by means of powdered ink and, as particularly described in the earlier specification, this is achieved by passing the copy surface through a body of powdered ink which is caused to vibrate in a hopper. Such a method isentirely satisfactory in itself but under certain circumstances other methods may be found more suitable and convenient.

The vaporizing agents or oils disclosed in my copending application are subject to evaporation or distillation when the original with which theyare in contact is heated. The oils are evaporated from the darker image areas on the original and the vapors are condensed on the copy member surface. The condensed oil constitutes the latent image which is to be developed. Suitable oils include odorless kerosene, essential oils, vegetable oils, glycerines, glycols, hydrogenated terphenyls and others having a suitable boiling pointor boiling point range and which do not injure the original to be copied.

Of the powdered, or particulate ink developing agents disclosed in my copending application, a mixture of pigment such as carbon black or colored powder and thermoplastic binder is particularly effective but other agents which will adhere to the ink-retaining image, such as metal powders and chemical materials, are also suitable.

The present invention is thus particularly concerned with the application of powdered ink to the surface of a copy sheet bearing an ink-retaining latent image. In the earlier specification this latent image is represented by areas of the vaporizing agent but other forms of latent image require development in a similar manner.

While the image on the copy surface is described as being latent, it is clearthat in view of the vaporizing [agents that may be used to create such a latent image, the ,image is latent in the sense that it is developable rather than in the strict sense that it is invisible. For example, an image created by deposition of glycerine may be discernible or indiscernible' to the unaided eye depending on the amount and purity of the glycerine and on the nature of the copy sheet. Although an image composed of glycerine is not, therefore, necessarily invisible, that image is developable according to the invention and it is to development of such images to which the invention relates.

According to the present invention a device for this purpose comprises guides defining paths for the copy sheet and for a transfer member carryingrpowdered ink, the paths running closely adjacent one another over an inking region in which is situated means for loosening'ink on the transfer member so as to facilitate its retention by the latent image. As a consequence the copy sheet only needs United States Patent to be fed round the path through the inking region where the latent image picks up powdered ink from the transfer member. The necessity for passing the copy Sheet completely through an ink reservoir is avoided thus improving the overall cleanliness and convenience of the process.

The transfer member may itself form part of the device, being constituted for example by an endless belt or roller so as to be capable of movement in a closed path and an ink reservoir for charging the member with ink may be situated in the path away from the inking region. As an alternative, however, the transfer member may be in the form of a previously inked strip which is fed from a supply reel along the path defined by the guides previously mentioned and thence to a take-up reel. Such a strip docs not form any part of the device itself since it functions in a similar manner to a typewriter ribbon, being used one or more times until the supply of ink is exhausted and then being thrown away and replaced by a fresh strip. AG cordingly the need for a separate ink reservoir is completely eliminated, thus adding to the overall cleanliness of the transfer process.

The powderedink carried by the transfer member tends to adhere to the surface of this member, and it is for this reason that the means for loosening the ink is provided in the inking region to facilitate the transfer of the ink to the latent image on the copy 'sheet.

acting directly on the ink-bearing surface of the transfer member. This doctor may for example be constituted by the edge of the ink reservoir, if one is provided, or by a blade or wire which serves as one of the guides defining the path of the transfer member.

The doctor may merely exert a scraping action on the transfer member, but the loosening effect is enhanced if the transfer member has a rough surface which cooperates with the doctor to create a vibration of the transfer member during movement of the latter. This'vibration helps to loosen'the ink and keeps it in a mobile condition once loosened. The loosening action may be. achieved merely by vibration without any scraping elfect by a doctor and for this purpose the transfer member may be in the form of an endless belt having a rough surface on the side opposite that carrying the ink. This surface then cooperates with a stationary member to create the necessary vibration. transmitted to the transfer member through the copy sheet by the provision of a member for supporting the copy sheet in the inking region and capable of movement in a closedpath, this member having, at the side away from the copy sheet, a rough surface which cooperates with a stationary member to create the necessary vibration as a result of relative movement between the two.

In another form of device in accordance with the invention utilizing the same general principle of loosening the ink from a transfer member the device comprises an endless strip having a rough surface on one side and which is movable round a substantially horizontal closed path defined between a pair of rollers having substantiallyvertical axes. The strip is folded on itself along its longitudinal axis over at least part of one of the horizontal runs between the rollers with thefold at the bottom and, the rough surface on the outside and the free edges of the folded portion separated to form a trough through which the copy sheet is guided and which has an ink reservoir towards one end. Preferably the strip is folded. along the whole of its length so that along one horizontal run the fold is opened to form the trough and on the return run the two folded portions lie fiat against one another. Since the return run is traveling in the opposite direction to that forming the trough the engagement between the rubbing surfaces produces a consider- Most simply the means for loosening the ink is in the'form of a doctor Altemately, the vibration may be able amount of vibration which maintains the ink in the trough in a free and mobile condition so that it may readily be picked up by the latent image on the copy sheet. In all of the embodiments of the invention, the means for loosening is effective to create a pool of loose and mobile ink particles supported by the transfer member which are contacted by the latent image on the copy sheet.

A number of constructions in accordance with the invention. will now be described in more detail with referencetorthe accompanying drawings all of which are diagrammatic views and in which:

FIGURE 1 shows a construction in which the transfer member is in the form of a roller;

FIGURE 2 shows a construction in which the transfer member is an endless belt and the ink reservoir is a perfo-ratedcylinder;

FIGURE 3 shows a construction in which the transfer member is a strip wound between a supply reel and a take-upreel with an ink reservoir in the form of a hopper;

FIGURE 4 shows a modification of the construction of FIGURE 3 for use with a pre-inked strip;

FIGURE 5 shows a modification of the construction of FIGURE 4;

FIGURE 6 shows a construction in which the transfer member is an endless belt to which vibration is applied from a support fora copy strip;

FIGURE 7 shows a modification of the construction of FIGURE 6 in which the support for the copy strip is in the form of an endless belt;

FIGURE 8 shows a construction in which the transfer member is an endless belt having a cellular compressible surface layer;

' partial elevation, respectively, of a construction in which the transfer member is an endless belt caus'edto vibrate by engagement with fixed members. I

Each of the devices shown in the drawings is intended either to form part of a complete copying machine such,

for example, as shown in FIGURE 1 of the application referred to above, or to operate independently as a defveloping unit. Accordingly, although various parts of .the different embodiments require to be driven,,no specific drives are shown in the drawings since it is assumed that the necessary drive will be provided by means of a belt, chain or. gear wheel from some other corresponding driven part of the machine or from a drive mechanism. It is not essential, however, that the machine should operate in accordancewith the method of the earlier application since the inking device of the present invention is suitable for the inking of various forms of ink retaining images. Whatever the form of machine with which it may be used, there will be a suitable drive mechanism for operating the inking devicesto be described. In each case, with the exception of the embodiments shown in FIGURES 5, 6 and 7 which are particularly suitable for the treatment of single sheets, the copy sheet is shown in the form of a continuous strip which is the case with the apparatus described in the earlier application. If individual copy sheets are to be treated, the continuous copy strip shown in the drawings is replaced by a suitable carrier for the sheets. 1 1

Referring first to FIGURE 1, the transfer member is in the form of a driving roller 1 having a smooth surface covering of a material such as silicone rubber, silicone- ,treated paper or plastic, or latex to which powdered ink tends to adhere in the form of a thin film. Powdered ink shown at 2 is contained in a reservoir in the form of a hopper 3 shaped to conform with the surface of the roller 1 and formed with.an extension 4 which constitutes a form of guard preventing the dispersal of the ink and maintaining the overall cleanliness of the device. The edge 5 of the hopper 3 bears lightly against the surface of the roller 1 so as to act as a doctor blade which has a slight scraping action and thus serves to loosen the ink on the surface of the roller and to form a small pool 6 of loose ink in a mobile condition. A copy strip 7 is driven to pass around a roller 8 so that its path runs closely adjacent to that of the roller 1 to constitute an inking region in the vicinity of the pool of ink 6. 'Consequently a latent image on the surface of the copy strip picks up powdered ink from the pool 6 and the developed image is indicated diagrammatically at 9. The opposite side of the copy strip does not come into contact with the powdered ink and only the part of the surface bearing the latent image picks up powdered ink so that a high standard of cleanliness is maintained.

In the construction of FIGURE 2 the copy strip 7 is driven to pass about a roller 8 situated adjacent a pool of powdered ink 6 defining an inking region. In this construction the transfer member is constiuted by an endless belt 15 which may for example be made of silicone-treated paper or plastic and which tends to pick up powdered ink in a similar manner to the roller 1. The belt 15 is driven in the direction of the arrows about rollers 16, 17 and 18 i which define part of its path, the remainder of the path being defined by a perforated cylinder 19 and a doctor blade 20. The cylinder 19 constiutes a reservoir for powdered ink 21 which passes outwardly through the perforations and forms a film indicated at 22 on the surface of the belt 15. This film is loosened by the action of the doctor blade 20 to constitute the pool 6 of mobile ink which is then transferred to the latent image to give a developed image 9.

In the construction of FIGURE 3 a belt shown as 25 is again used but in this case it is not an endless belt.

The belt 25 is driven from a supply reel 26 to a take-up reel 27. When the whole of the strip has been transferred to the reel 27 it can either be rewound prior to further use or alternately thereels 26 and 27 can be interchanged. The copy strip 1 passes around a roller 8 through a pool of mobile ink 6. Theink is supplied to the surface of the belt 25 from a hopper 28. The pool of ink 6 is con stituted by ink loosened by means of a doctor blade 33 which, together with the rollers 31 and 32, defines the path of the strip between the reels 26 and 27. This construction leads to a result similar to that already dcscn'bed in connection with FIGURES 1 and 2.

Instead of providing an ink reservoir 28 the belt 25 may be replaced by a pre-inked strip which may be used a number of times and then thrown away in the manner of a typewriter ribbon. Such a strip may for example be formed of latex, silicone-treated paper, plastic or grosgrain to which it is found that powdered ink will adhere without becoming appreciably loosened during the storage of the reel of strip. The scraping action of the doctor blade 33 readily provides a pool of mobile ink as already described.

FIGURE 4 illustrates specifically a construction using such a pre-inked strip and having no reservoir for powdered ink. The strip 34 is led from a supply reel 35 to a take-up reel 36, passing about a pair of guide rollers 37 and 38 and a pair of doctor wires 39. The strip 34 passes in a horizontal path of travel between the doctor wires 39 and this provides an inking region. The copy strip 7 passes around rollers 40 and 41 defining a corresponding horizontal path, the strip being backed, over the horizontal portion of its path, by a plate 42. The drive to the strip 34 is such as to produce rapid forward and reverse movement of the strip; for example the strip may move forw ard and backwards in steps equal to the width of the inking region with periodic additional forward steps of A or so. As a consequence the strip is gradually fed from the reel 35 to the reel 36, but executes a rapid to-and-fro movement as indicated by the arrow 43. Each of the doctor wires 39 alternatelyproduces a pool of mobile ink'44 according to the direction of travel of the strip and as a result a layer of ink is caused to move back and forth over the whole horizontal portion of the strip 34 between the doctor wires 39, thus permitting an effec tive transfer of ink to the copy strip 7.

The construction of'FIGURE 5 operates onthe same principle as that of FIGURE 4, but includes some of the structural features of FIGURE 2. A pair of doctor wires 39 produces pools of ink'44 as the result of to-and-fro movement of a belt 45, made of silicone-treated paper or plastic, or grosgrain for example. The belt 45 passes around an ink reservoir in the form of a perforated cylinder 46 and the remainder of its path is defined by guides formed by shaped projections from a unitary member 47, which also supports the cylinder 46. The member 47 is formed of a material having a high slip surface such as polytetrafiuoroethylene, so that the need for individual rollers is avoided.

As. shewn, the device is intended for the inking of individual sheets which are supported by carrier wires 48, guided by rollers 49. The fact that the copy material travels in a straight line makes this construction particularly suitable for the inking of individual sheets, although a continuous copy sheet can, of course, replace the wires '48. The inking region is defined by the horizontal part of the path of the'belt 45, over the whole of which ink is maintained in a mobile condition as described in connection with FIGURE 4. I

In addition to the scraping action of the doctor, whether in the form of a blade asshownin FIGURES 1, 2 and 3 or a wire as shown'in FIGURES'4 and 5, a certainamount of vibration of the transfer member is produced. This wibration' by itself may be sufiieient to loosen the ink without the need for a doctor and this principle is il1ustrated by FIGURES 6 and 7. In .the construction of FIGURE'G thetransfermember is inthe form of an endless belt 50 driven around rollers51 52 and 53' and ink is supplied to it from a hopper 54. The copy strip 7 passes around a support in the form of a hollow cylinder 55 having a roughened internal surface as shown at 56. This cooperates with a stationary member 57 to produce a vibration of the cylinder 55 which is transrnitted through the copy strip 7 to the belt 50thus loosening the powdered ink to provide a pool of ink in a mobile condition and facilitate transfer of thevink to the latent image on the strip 7, while at the same time preventing adhesion of excess ink;

A similar'result is achieved by the construction of FIG- URE 7 in which the belt 50 is guided by rollers 60,61, 62 and 63. In this case a slightly different form of ink reservoir is shown, constituted by a closed container 64 having entrance and exit slits 65 and 66, respectively. The powdered ink is shown as 67 and the belt 50 is guided through the container by means of a rod 68 so that only its upper surface comes into contact with the ink 67. The copy strip 7 is supported by an endless belt 70- capable of movement in a substantially triangular path'defined by rollers 71, 72 and 73. This belt has a roughened internal surface 74 cooperating with two stationary. members 75 to produce a vibration which is transmittedto the belt 50 and thus serves to loosen the ink in the manner already described in connection with FIGURE-5. In each of these last two constructions the cop strip 7 may be replaced by' a carrier'belt for individual copy sheets.

In the construction of FIGURES the transfer member is constituted by an endless belt having a cellular compressible surface constituted, for example, by soft rubber or polyurethane foam. Ink is supplied to the belt 80 from a hopper 81 and collects in the open cells of the material. The layer of ink carried by the belt is thus discontinuous. The guide rollers for the belt 80 are omitted for simplicity, its path being indicated by the arrow 82. At the uppermost point of its path, however, the belt passes around a stationary member 83 so that the tension at this point tends to compress the surface of the belt and thus to loosen the ink by ejecting it from the cells to form a pool of mobile ink 84. Immediately following the inking region is a blade 85 against which the powdered ink tends to collect and which thus causes the residue of the ink to re-enter the cells and to be carried round by the belt 80. The copy strip 7 passes about a roller 8 so as to dip into the pool of mobile ink 84 in the manner previously described.

In the construction of device shown in FIGURES 9 to 11 a transfer member is formed by an endless strip 96 which is folded on itself along its longitudinal axis as best seen in FIGURE 9. This material is formed on its outer surface with transverse ribs 91 seen in FIGURE 9 and illustrated diagrammatically in FIGURE 10. The stri may for example be formed of grosgrain which has ribs of a suitable size. The folded strip is driven around a substantially horizontal path defined by a pair of rollers 92 turning about vertical axes. As can be seen from FIGURES 9 and 11 the fold in the strip is at the bottom and in one of the horizontal runs between the rollers 92 the free edges are separated by a spacer 93 to form a trough within which the copy strip 7 is guided by a roller 94. On the return run, the folded portions indicated as 95- inFIGURE 11 lie flat againstone another but the right-hand surface as seen in FIGURE 11 engages the corresponding left-hand surface of the trough formed by the other run. Since these surfaces are moving in opposite directions the engagement between the two produces a degree of vibration as can best be understood from I FIGURES 12 and 13 show a final form of device in which the transfer member is formed by an endless belt passing around rollers 101 and having ribbed surfaces I 102 which may for example be fogmed'of grosgrain as previously mentioned. Powdered inkis supplied from a hopper 103 and the belt 101 iscaused to vibrate over the greater part of its upper run by means of stationary blades 104. The copy strip 7 is led around a guide member 105 so as to pass closely adjacent the belt 101 over the region of vibration in which the ink is maintained in a mobile condition so as to be transferred to the latent image in the manner previously described.

I claim:

1. A device for applying powdered ink to a copy surface having a latent image comprising an ink-retaining substance, said device comprising means to guide a copy surface in a first pre-determined path in said device; means to guide a powdered ink supply member bearing a layer of powdered ink thereon in a second pre-determined path in said device; said first and second paths being closely adjacent at an inking region in said device and disposed such'that, when the device is operative, at least a portion of said copy surface is located above said powdered ink supply member at said inking region; and. ink release means cooperatively arranged to loosen by mechanical action only powdered ink disposed on said powdered ink supply member to form a pool of loose and mobile ink particles at said inking region, said loosened particles being supported on said powdered ink supply member and disposed between said powdered ink 2. A device as claimed in claim 1 wherein said powdered ink supply member comprises a cellular, compressible surface for the reception of powdered ink.

G. A device according to claim '1 wherein said means to guide a powdered ink supply member comprises a supply reel and a take-up reel and said powdered ink supply member is in the form of a strip extending between said supply reel and said take-up reel.

4. A device according to claim 1 wherein said ink release means comprises means to vibrate the powdered ink supply member.

'5. A device according to claim 1 wherein the powdered ink supply member has a roughened surface and wherein the ink release means comprises a stationary member 'which' cooperates with said roughened surface to vibrate the powdered ink supply member during movement of the latter. I

6. A device according to claim 5 wherein the stationary member is a doctor cooperatively arranged to loosen by mechanical action only powdered ink disposed on said powdered ink supply member.

,7. A device according to claim 1 wherein said ink release means comprises means to vibrate the copy surface to thereby vibrate said powdered ink supply member.

8. A device for applying powdered ink to a copy surface bearing a latent image comprising an ink-retaining substance, said device comprising means to guide a copy surface in a first pre-determined path in said device; means to guide a powdered ink supply member bearing a layer of powdered ink on a surface thereof in a second pre-determined path in said device; said first and second paths being closely adjacent at an inking region vin said device and disposed such that, when the device is operative, at least a portion of said copy surface is located above the ink-bearing surface of said powdered ink supply member at said inking region; and ink release means comprising a doctor cooperatively arranged to loosen by mechanical action only powdered ink disposed on the surface of said powdered ink supply member to form a pool of loose and mobile ink particles at said inking region, said loosened particles being supported on said powdered ink supply member and disposed between said ink-bearing surface of said powdered ink supplymember and said copy surface such that, during operation, mobile ink particles of said pool are brought into contact with and adhere to said ink-retaining substance on said copy surface at said inking region.

9. A device for applying powdered ink to a copy sursubstance, said device comprising means to guide a copy surface in a first predetermined path in said device; reservoir means to store a supply of powdered ink; means to supply powdered ink from said reservoir means to a powink supply member bearing a layer of said powdered 'ink thereon in a second pre-determined path in said device; said first and second paths being closely adjacent at an inking region in said device and disposed such that, when the device isoperative, at least a portion of said copy surface islocated above said powdered ink supply member; at said inking region; and ink release means cooperatively arranged to loosen by mechanical action only powdered ink disposed on said powdered ink supply memher to form a pool of loose and mobile ink particles at said inking region, said loosened particles being supported on said powdered ink supply member and disposed besurface such that, during operation, mobile ink particles of said pool are brought into contact with and adhere to said ink-retaining substance on said copy surface at said inking region.

'10. A device according to claim 9 wherein said ink release means is a doctor comprising an edge of said reservoir.

'11. A device for applying powdered ink to the surface of a copy sheet bearing an ink-retaining latent image of an ink-retaining substance, the device comprising an endless strip having a rough surface on one side and which deredink supply member; means to guide said powdered .45 face bearing a latent image comprising an ink-retaining tween said powdered ink supply member and said copy is movable in a substantially horizontal closed path defined between a pair of rollers having substantially vertical axes, the strip being folded on itself along its longitudinal axis over at least part of one of the horizontal runs between the rollers with the fold at the bottom, the rough surface on the outside and the free edges of the folded portion separated to form a trough through which the copy sheet is guided, an ink reservoir located adjacent one end of said trough and providing a supply of ink on the walls of said trough, said trough being of such a width that the side adjacent a second of said horizontal runs of said strip bears against the rough surface of the latter, so that when said strip is driven about its closed path the engagement between the two rough surfaces moving in opposite directions produces a vibration serving to loosen theink from said walls of said trough to provide a pool of loose and mobile ink particles for dc veloping said latent image on said copy sheet.

12. A device according to claim 111, in which said strip is folded along the whole length.

13. A device according to claim 11 in which said strip is formed with transverse ribs which engage one another to produce the vibration.

14. A device for applying ink to the surface of a copy sheet bearing an ink-retaining latent image of an inkretaining substance comprising: reservoir means to store a supply of powdered ink; first conveyor means to convey a first endless belt member along a'first path; second conveyor means to convey a second endless belt member along a second path such that a portion of said second path is in close proximity to a portion of said first path at aninkiug region and disposed such that, when the device is in operation, said portion of said second path is disposed below said portion of said first path, said second path extending to said reservoir means to enable said second belt member to carry a thin layer of powdered ink from said reservoir means to said inking region; means to feed a copy sheet bearing an ink-retaining latent image into contact with said first belt member, means to maintain said copy sheet adjacent to said first belt member such that the copy sheet is conveyed through said inking region; ink release means at said inking region cooperatively arranged to loosen by mechanical action only powderedink disposed on said second belt member to form a pool of mobile ink particles supported by said second belt member and disposed between said first and second belt members whereby a copy sheet on said first belt memberis contacted with ink particles of said pool at said inking region; and means to separate said copy sheet from said first belt member.

15. A device according to claim-14 wherein said second endless belt member comprises,'on a surface disposed away from said first endless belt member, a rough surface and wherein said ink release means includes a.

stationary member which cooperates with said your surface to impart vibration to said second endless belt member.

.16. A device according to claim 14 wherein said reservoir means comprises a closed container having entrance and exit slits for said'second endless belt means and guide means to guide said second endless belt member therethrough such that only one surface thereof contacts said powdered ink.

'17. A method of developing a liquid, ink-retaining latent image on the surface of a copy sheet comprising 7 9 layer of powdered ink particles to an inking region on a movable ink carrying supply member, removing, by mechanical action only, the ink particles from the ink carrying supply member to maintain a pool of mobile ink particles at said inking region supported by said ink carrying supply member, and moving the latent image surface of the copy member in contact with mobile ink particles of said pool to allow ink particles to adhere to said inkretaining substance on said copy surface at said inking region to develop said latent image.

1 References Cited by the Examiner UNITED STATES PATENTS 2,503,759 4/1950 Murray 1173.4 X 2,732,775 1/1956 Young et a1 95--1.7

2,808,777 10/1957 Roshkind 10114-9.2X

15 WILLIAM D. MARTIN, Primary Examiner.

G. L. HUBBARD, Assistant Examiner. 

17. A METHOD OF DEVELOPING A LIQUID, INK-RETAINING LATENT IMAGE ON THE SURFACE OF A COPY SHEET COMPRISING THE STEPS OF CONVEYING POWDERED INK PARTICLES TO AN INKING REGION ON A MOVING ENDLESS BELT, REMOVING, BY MECHANICAL ACTION ONLY, THE INK PARTICLE FROM THE BELT AT SAID REGION TO MAINTAIN A POOL OF MOBILE INK PARTICLES SUPPORTED BY SAID ENDLESS BELT, AND MOVING THE LATENT IMAGE SURFACE IN CONTACT WITH MOBILE INK PARTICLE OF SAID POOL TO DEVELOPE SAID LATENT IMAGE. 